Barr body: the color-staining spot (the sex chromatin) located at the edge of the nucleus of cells taken from individuals with more than one X chromosome. It is normally found in female cells, and so is used as a sign of female genetic sex. It is also found in men with the 47,XXY (Klinefelter's) syndrome. It is missing in girls with the 45,X (Turner's) syndrome. The Barr-body test is rapid and inexpensive as compared with actual chromosome counting, and so is used as a method of preliminary X-chromosome screening.

Dictionary of Sexology Project: Main Index